To improve automobile interior silence, sounds of automobile exterior (including engine sound, sound of tire squeal of automobile while running or the like) are made absorbed by porous material, or composite material made of resin-sheet like-surface skin adhered to fiber material such as a flexible polyurethane foam or felt is arranged on rear-surface side of a member configuring a wall of the automobile interior (Patent Literatures 1 and 2).
Here, FIG. 5B schematically shows sound absorption characteristics (relationship between frequency of incident sound and sound absorption ratio) of a soundproofing material 1′ when sound is made to be incident into the plate-like soundproofing material 1′ composed of an urethane foam, as illustrated in FIG. 5A, for example. That is, sound absorption ratio with respect to sound regions excluding the high sound region depicted in shades in FIG. 5B is lowered.
As shown in FIG. 6A, in the case of a soundproofing material 1″ combining an urethane foam 1a″ with a resin sheet 1b″, absorption ratio of sound regions excluding the middle sound region depicted in shades in FIG. 6B is lowered.
As such, on the one hand, an enhancement of high sound absorption performance in a limited sound region is enabled, on the other hand, by using the conventional soundproofing materials, a high sound absorption performance throughout a wide frequency band cannot be provided.
In view of the above, an automotive soundproofing material capable of providing high sound absorption performance throughout a wide frequency band has been in demand.